The present invention is based on an input device according to the species defined in the main claim. Input devices, for example, for navigation systems in a motor vehicle, are already known, in which letters of the alphabet are input using as few operating elements as possible, and individual alphabetical letters are chosen by a user from a selection of letters. Furthermore, mobile computers (so-called laptops) may be used in the motor vehicle. Such mobile computers have a keyboard, which corresponds in general to the keyboard of a conventional computer, by which text may easily be input, for example, for a route-determination program running on the mobile computer. However, a user must carry the mobile computer along in the vehicle, fix it in position for operation, and take the mobile computer again when leaving the vehicle, or protect it from the view of people looking into the vehicle from the outside, so as not to create a theft incentive.